For printing in a solid-ink printer, a common method of applying droplets of ink onto a piece of paper is to directly print the image onto the paper, i.e., a process known as direct printing. Ink jet printing systems utilizing intermediate transfer ink jet recording methods, such as that disclosed in U.S. Pat. No. 5,389,958 entitled IMAGING PROCESS and assigned to the assignee of the present application is an example of an indirect or offset printing architecture that utilizes phase change ink. A release agent application defining an intermediate transfer surface is applied by a wicking pad that is housed within an applicator apparatus. Prior to imaging, the applicator is raised into contact with the rotating drum to apply or replenish the liquid intermediate transfer surface.
Once the liquid intermediate transfer surface has been applied, the applicator is retracted and the printhead ejects drops of ink to form the ink image on the liquid intermediate transfer surface. The ink is applied in molten form, having been melted from its solid state form. The ink image solidifies on the liquid intermediate transfer surface by cooling to a malleable solid intermediate state as the drum continues to rotate. When the imaging has been completed, a transfer roller is moved into contact with the drum to form a pressurized transfer nip between the roller and the curved surface of the intermediate transfer surface/drum. A final receiving substrate, such as a sheet of media, is then fed into the transfer nip and the ink image is transferred to the final receiving substrate.
When the transfer roller is fully engaged with the imaging drum, it may apply a load upwards of 500 lbs in a relatively short period of time. The addition and removal of such a load in such a period of time may cause the velocity of the imaging drum to deviate, resulting in a transient rotational disturbance of the drum. Additionally, there may be a steady state velocity change due to the load. The imaging drum servo control system may be insufficient to accommodate these velocity deviations, resulting in image mis-registration, or other undesirable effects, referred to as motion quality problems.
Currently, when performing marking operations that require multiple passes, the processes of forming the image on the imaging drum and transferring the image to the media are performed sequentially. The imaging must be completed before beginning the transfer process because of the motion quality problems associated with engaging the transfer roller with the imaging drum after the image has been formed on the imaging drum. As a result, productivity is limited by performing the imaging and transferring operations in series. When using an imaging drum that is large enough to hold more than one image, also referred to as a pitch, the image formed on one pitch must be transferred before an image may be formed on another pitch.
Still other aspects of the present invention will become apparent to those skilled in the art from the following description, wherein there is shown and described a preferred embodiment of this invention by way of illustration of one of the modes best suited to carry out the invention. The invention is capable of other different embodiments and its details are capable of modifications in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive.